The invention relates to a method for operating a communication system comprising one or more transmitters and receivers, in which the transmitted signals are provided with a preamble for training the receiver and/or the transmitter being in communication.
Such a method is known from “IEEE 802.11b Wireless LAN standard”. In this known method a preamble in transmitted signals is always needed, the length of the preamble needs not be fixed. If the propagation conditions are good, the preamble may be short, just enough to set the receiver parameters like frequency and timing offset. In worse conditions the detection of the signal may be difficult and training the receiver by means of the preamble may be even more difficult. In the latter conditions a longer preamble may help to train the receiver because of the possibly longer training period.
In recent communication systems higher data rates are introduced, impulsing the need for short preambles.
In known systems the problem is encountered that the receiver will not know for certain that a received signal will have a long or short preamble and whether the propagation channel will be good or bad, needing a short or long preamble respectively.
The invention has the object to provide a method of the above mentioned kind, in which the above mentioned problems are obviated such that with a tolerable detection quality the preamble having the as short as possible length is choosen and that thereby the throughput of the data is as high as possible.